Hydraulic pump and motor



May 19, 1953 E. H. JOHNSON HYDRAULIC PUMP AND MOTOR Filed Feb. 15, 1951s Sheets-Sheei 1 Inventor Attorney May 19, 1953 Filed Feb. 15, 1951 E.H. JOHNSON HYDRAULIC PUMP AND MOTOR 3 Sheets- Sheet 2 y 9, 1953 E. H.JOHNSON 2,638,848

HYDRAULIC PUMP AND MOTOR Filed Feb. l5, 1951 3 Sheets-Sheet 5 Reser 1/0)I Pump Inventor Attorney Patented May 19, 1953 UNITED STATES PATENTOFFICE HYDRAULIC PUMP AND MOTOR Edward Harry Johnson, Coventry, England,as-

signor to The Keelavite Company Limited, Coventry, England, a company ofGreat Britain Application February 15, 1951, Serial No. 211,118 In GreatBritain February 16, 1950 13 Claims. (01. 103-42) hydraulic fluidthrough the working clearances referred to and, in some cases, ofreducing the unbalanced thrusts acting on parts of the mechanism of thepump or motor.

One example of such a pump or motor is described in the specification ofUnited States Patent No. 2,483,705. X

The invention is particularly but not exclusively applicable tohydraulic motors of thelkind usually called sensitive motors, that isto. say motors which are required to rotate at aspeed closely related totheir consumption of hydraulic fluid (i. e. the rate at whichhydraulic'fiuid is permitted to pass through them) and to maintain anexact relationship between speed andffluid consumption down to very lowspeeds, such motors being used, for example, for training and elevatingguns and for similar purposes.

It will be seen that with pumps or m'otors'of the kind referred to asdescribed in United States patent specification No. 2,483,705 having apressure control valve which maintains the hydraulic pressure within thecasing at a value between the inlet and outlet pressures of the pump ormotor and preferably midway between these pressures, there will be agreater flow of fluid into the casing than out of the casing through theworking clearances during part of each revolution of the motor and agreater fiow of fluid out of the casing than into it through the workingclearances during another part of each revolution of the motor,according to the proportions of the working clears ances which, atdifferent points in the rotation of the motor, are subject respectivelyto the'pressures on the high and low pressure sides of the motor, therebeing alternate flow into and out of the casingthrough the pressurecontrol valve. In other words, the fact that the'pressure control valvemaintains a constant pressure within the casing means that the rate offlow of fluid from the working chamber through the parts of the workingclearances subject to high pressure varies with the variations in thelength of such part or parts ,of the working clearances occurring duringeach revolution of the pump or motor.

the motor.

Moreover, similar changes in the rate of flow through the workingclearances with variations in the lengths of the parts of the Workingclearances subject respectively to high pressure and low pressure wouldoccur in other types of hydraulic pumps or motors of the kind referredto having a pressure control valve maintaining a pressure in the casingbetween the pressureson the high and low pressure sides of the pump ormotor.

At high motor speeds when the quantity tr fluidflowing through the motoris high the variations in the rate of escape of fluidthrough the part orparts of the working clearances subject to the pressure in the highpressure part or parts of the working chamber or chambers have littleeffect since the maximum rate of escape is'only a very small proportionof the total flow through When, however, the rate of flow through themotor is small it will be seen. that the variations in the rate ofescape vof fluid through the part or parts of the working clear; ancessubject to the pressure in the high pres: sure part or parts of theworking chamber or chambers will have an appreciable efiect and in factthat, if the rate of flow through the motor is reduced to a point atwhich it approximately equals the rate of escape of fluid through thepart or. parts of the working clearances subject to high pressure at therotational position of maximum escape the motor will come to a stop.

at this position.

' The object of the present invention is to overcome this difiicultyandto provide a pump or motor in which the speed of rotation will beclosely allied to the rate of fluid flow through the pump or motor overthe whole working range.

including especially the low speed and flow range.

To this end a hydraulic pump or motor of the kind referred to accordingto the present inven-' tion, instead of having a pressure control valvesuch as is employed in the form of pump or motor "described in thespecification of United States Patent No. 2,433,705, has a closed casingwhich flow of fluid into the casing from the high pressure side of thepump or motor and out of the casing to the low pressure side would begreater than the normal steady load working pressure for which the pumpor motor is intended, but preferably less than the maximum pressurewhich the pump ormmotor and...,the, apparatuswith whichdit is tobeiusedbis desig-ned.-.towithstand-so thattthe valves will act togetheras safety valves preventing the occurrence of dangerous hydraulic loadson the pump or motor or its associated apparatus.

Moreover, it will generally be preferredttorpro vide non-return valvesconstructed and arranged so that they will open under peak pressureconditions in the apparatus withnwhichtthe.purppor motor is associatedand in fact at a pressure appreciably below the peak pressuraw-hichwould occur during working of the apparatuswerethe non-return valves notprovided so that .awperiodic opening of the valves and consequent flowof fluid through thecasing will becausedautomatica'11y..at; intervals,during operation; of,the apparatus.

"'Whenlas willjoften be'the cas e,lthe,pump or motor is intended tooperate. ,in' either direction and/onto act alternatively, as, a, pumpor motor, "the ,nlon-return. valves. are preferably duplicated so asitoprovide a pair of non-return valves arranged to function. in the*de'sire'd manner irrespect'ive of the direction of operation of thepumpor motor or of whether it, is at. the ,moment serving the purposeofa;,pump .or, vmotor. Thus in "such. an "arrangement" there would beprovided two pressureoperated non-return valves disposed respectivelybetween .the' interior of. the

casing andthe-inietandoutiet portsof the pump pressures-required'tocause opening of anon-return"valve*permittingifiow' of fluid from one ofthe-po'rts intoifthe teasing and open ng ofthe asso'ciatedynon-returnvalvepermittingi fiow of fluid-out of the" casing to the'other port"exceeds the-difference "between the pressures" in the twoportvduring-thenormal steady load working ooriditions'with the pump ormotorg'operatingiin the appropriate direction.

It will' be understood in" this connection that the-pressure-difierencerequired to'cause'ithe two appropriate non-return-v'alvesto open, whenone port -is" at the-higher pressure-may be the same 'as or differentfrom 'that'required to cause opening'of the other" two 'non returnvalues when -the other port is; at the 1 higher pressure.

The; invention may be applied to; pumpsand motors' ofthe kind referredto' of various kinds but'one 'arrangcmentaccording to the inventionapplied to a rotary pump orwmotor of."the vsocalledrotary abutmendtype.is shown by Way of ejX'am'ple'inthe accompanying'drawings; in which"Figure' 1 isia sectional side. elevationgofthe pump .or' motor,

fiEigure'Z is. a cross sectional view {of the pump ormotor inthe;planexindicatedby the line2 2 n'F 'e *Figureii is a sectionalplan'on angehlarged scale, showing the. arrangement of; non-returnvalves provided in .itheypump or motor shown in 'Eigures 1 and 2,and

Figure 4 is a diagrammatic illustration of a hydraulic systemincorporating a pump or motor according to the invention.

In the construction of pump or motor shown in Figures 1, 2 and 3, thepump or motor is of known general type comprising a fluid-tightcaslihgaAuvithincwhich are. mounted. the v parts of it'hefpumpcor motorenclosing thezsworleing chamber. These parts comprise an outer part or.,housing B having formed therein two intersecting cylindrical bores B13 constituting respecitivelytitheaouter circumferential wall C of anannular.,working chamber C and the principal part ?.'.D =of"the*circumferential wall of a rotary abut- ..ment.-.'chamber. jSecured toone end of the housing part B is an inner part E which forms one=end':awall ffi eofuthe working chamber C the in-ner circumferentialWall C of the working cham-beciand the smaller part D of thecircumferential wall of the abutment chamber. Securedyto thepther end of.the housing part B is, an end'rplatefF which closes; the adjacent ,endor ,the abutment chamberD,'D -.an'd has anyaperture thereinzcoaxialwith.and of the samefdiameter as .the outergcircumferential wall Ooffitheworking :"chamber; while a ring F coaxial with andgof. the same:externalzdiameter as the inner circumferential walr C .of the working..chamber is also secured to the housingiB so thatthere isan annularslot between thejparts F and'F .of ithe same" cross sectional dimensionsas the .working chamber.

TCarried' in hearings Gand' G in: the partsjjfE and? is a rotor assemblycomprisin aJSha'itFH to which is keyed a r0tor"I-I compri1sing a.disclike ,portionili f from which extends a; cylindrical flange-likepart'frl which liesiwithinand makes a close sealing. fit with the innerandyoutertcircuniferential walls vofthe; annular slot between "the partsF and? g and itself carries',two' blades H which extend across theworking chamber and makea sealingffit with its'inner .and outercircumferentialwallsi'C, C anclthe. end wallf'c The 'shaftf'I-I extendsithroughaflnid-tight gland ffi in the casing A.

Mounted Withinthe abutment chamber is a rotary zabutment J havingtWO'blade-receiVing recesses J thereinfthis abutment being mount- ,ed ona sh'aftJ supported in' bearings 1 37 in thegpartIE;andifdriven,"soas torotate at; the same speed asbutinithe QPposite directiorrgfrom therotort'Hi;.through gearingK.

"Inlet: and outlet ports" L, Mopening' into the working. Chamber.respectively on the two sides of the abutment'J communicate respectivelywith inlet. and; Qut1et ,passases; L and M Assmniu thejdevice. ,togbeyinoperation has a ,,pump, as the rotor, and abutmentrotatethejiiuidis,drawnirom onaof' the passagesiL 011M by the .bladesand deliveredthrough thero'ther and;.'the abutment, while"maintaining,a,seal at all ,times acrcssfthe working chamber .between the, inlet .andoutl p rtscomes into position ,fonone of its blade receiving recesses Jto receive, a, blade andflpfirmit such; blade to pass the abutmentat,the.appropriate times.

"Pressure; balancin recesses and pas a e are ShQWn associated With "the,.abutment' blllix i fl theseand; the general functioningjof devices ofthe kind shown arelmown they willnotbe further;;describcd.

'j -M0unte'd onthe housing part B is a va1v :,.hous ingN containing .twoparallelbores one of? which c0mprises...a,centra1 s ction 0, of,relativel small diam t penin byway of. con calyal eseatines O into endportions 0 ,0 of relatively large diameter while the other, P, is ofapproximately thesame diameterthroughout its length apart from suchsmall differences in diameter as will be apparent fromFigure 3 of thedrawings. The ends of the bores 0, 0 -O and P are closed byscrewthreaded caps Q.

Communicating with the central part 0 of the bore 10, O 0 is one end ofa passage R the other end of which communicates with the interior of thecasing A at its highest point as shown in Figure 1. Similarlycommunicating with the central portion of the bore P is one end of apassage S the other end of which communicates with the interior of thecasing A at a point displaced from its highest point. One pair ofadjacent ends of the two bores O, 0 O and P communicate with a commonpassage T opening into the passage L while the other pair of adjacentends of such bores communicate with a passage U opening into the passageM Associated with each of the valve seatings O and O is a ball valve V,V normally maintained in contact with its seating by a spring V actingthrough a thrust member V Mounted in the :"bore P on opposite sides ofthe passage S are two valve seating members W, W making fluid-tightjoints with the surface of the bore, ,these valve seating members beingprovided with bores W W terminating in valve seatings at their adjacentends in contact with which ball valves W, W are normally maintained by aspring W acting through thrust members W".

It will thus be seen that ifthe pressure in the passage L or the passageM rises sufficiently relatively to the pressure in the casing A thevalve W or W as the case may be will be lifted by pressuretra nsmittedthrough the passage T or U so that fluid will flow into the casing Athrough the passage 8. Also if the pressure in the casing A risessufliciently relatively to that in one or other of the passages L offluid into the casing A, one or other of the valves V or V will open,that is to say whichever of these valves leads to the passage T or U forthe time being, at lower pressure.

In practice the casing A is filled with working fluid and it will beseen that, assuming that there is no air space in the casing A, thepressure in one or other of the passages L or M must rise sufficientlyto cause opening of the appropriatevalve W or W and of the associatedvalve V or V before the valves in question will open to permitsimultaneous flow of fluid to the casing A through one of ,the valves Wor W and from the casing through the appropriate one of the valves V orV It will moreover be apparent that the opening of the two appropriatevalves and the corresponding flow of fluid into the casing A through thepassage S and out of the casing through the passage R will take placewhenever the pressure in either of the passages L or M exceeds that inthe other by an appropriate amount.

The pressure difference required to cause opening of the valves W and Vmay or may not be the same as that required to cause opening of thevalves W and V Usually, however, the arrangement and setting of thesprings V V and W will be such that approximately the same pressuredifference causes the appropriate two valves to open, whether the higherpressure is in the passage L1 or in the passage M Preferably, moreoverthe spring W is of such effective strength relative to that of thesprings W and V that approximately the same pressure difference or M dueto such delivery is required across each of the'four valves to open it.Thus whenever a pair of valves opens the pressure within the casing A isapproximately half Way between the pressures in the passages L and M Thedimensions of the parts and the forces exerted by the springs arepreferably so determined in relation to the characteristics of thehydraulic apparatus with which the pump or motor is to be used thatwhile during normal steady load operation the valves remain closed, theappropriate pair of valves will open each time peak working conditionsare experienced so that each time such peak working conditions occur,fluid Will be causedto flow into the casing through the passage 8 andout of it through the passage R. In this way not only does the valveapparatus act as a safety valve to prevent the apparatus being subjectedto excessive hydraulic loads but should there be any tendency for air tocollect in the highest part of the casing A it will beejected throughthe passage R. Thus the casing tends to be maintained completely filledwith liquid. In this way, as explained earlier, leakage and variationsin such leakage through the working clearances between the partsconstituting the working chamber tend to be reduced.

One particularly useful application of the invention is to a sensitivepump or motor constituting part of a hydraulic power transmission systemfor moving intermittently heavy apparatus, for example a gun or gunturret wherein there may be heavy peak loads when starting and stoppingthe apparatus with periods of normal steady load between them.

One such hydraulic system is shown diagrammatically in Figure 4, inwhich the system comprisesa hydraulic fluid reservoir X from which asuction passage X leads to the inlet passage M of a hydraulic pumphaving an outer casing A and constructed as shown in Figures 1, 2 and 3.The outlet passage L of this pump leads through a pressure line X to theinlet port of a control valve Y of the known rotary type having a rotarydistributing valvemember Y controlled by suitable mechanismdiagrammatically shown at Y The valve Y has on the one hand twoalternativepressure outlet passages Y Y leading re--v spectively t theinlet and outlet passages M and L of a hydraulic motor having a casing Aandalso constructed as shown in Figures 1, 2 and 3, and on the otherhand two relief passages Y leading to the reservoir. Since the valve Ywill be of well known form and in itself constitutes no part of thepresent invention it will not be further described or shown.

The hydraulic motor is connected by suitable transmission mechanism to aload indicated at Z having a considerable inertia such for example as agun or gun turret.

In operation the pump delivers hydraulic fluid continuously from thereservoirX to the control valve Y which in its central or neutralposition closes both the passages Y and Y and opens the passage X to thepassages Y so that the pump merely circulates fluid freely.

When the valve member Y is moved in one direction or the other from suchcentral positionit progressively closes communication between thepassage X and the passages Y while opening one or other of the passagesY or Y to the pressure line X and the other of these two passages to oneof the relief passages Y Thus the motor is caused to rotate in onedirection or the other according to the direction in which, the

memberfi rhas sheen moved. from: its :central position.

*izSincetLtha zload' Zv has; substantial;inertiaathe suddemmovementaofz. .the;.memb;er cause peak pressures to be built up in theappropriate one ef :the passages=Y 3.01 Y .beioresithe; inertia ofntheloadsisnovercome: ands'undensuch-condi tionsitthe 'appropriate: pair ofnon return valves Wiaxand'iVL or'nW :and-ilFWould ,open: to :limit' thehydraulic load. isimila rly ifizithe control member Y 1. -is..sudden.lymoved: torstoprimovementooi the load'zj Z-.'the momentum lot .the. loadmay :build up awpeakapressure in; the a appropriates one of the passagesY or" Y awhichl-isiz then closed by" the valve-,2anclizthe:other':appropriate-main ofmonreturn valves :in themotordwillwopen. *rMoreover, each: time this occurs; any: air in thecasing of the pump'will bezegieotedthrouglr the passage R. 5 :Thetnon-retumn 1 valves :would sh'OWBVETbEECOIlstruct'ediand arranged soathatizunder normal steadya-rload conditions; thatiis ito= say zwheirtthe loadiizuisz sbfiillg moved: at: other than approximately maximumracceleraition and .is znotrhaving approximately :inaximum'deceleration z'imposed upon'rit the:-non.+return valveswilrremainuclosed.

nIt Willi the; appreciated :that; ;.a1-though: :for convenience thespumphasbeen;describediasaofcthe kindishownziniFsigures 1 2.a-nd 3xit=neednotnecessarilyhbes provided with :nonereturn valve -;.apparatu sacoordin'g'jto the: :invention.

vmhatl In claimaasz any? invention. 2 and Z desire" :to securezbyiLattersPatent; is:

'11 rotary -.hydraulicamachinecomprising =relatii'elyamovingiparts'enclosing aworlsing chamber with working clearances between? therelatively I moving pants and inlet and outlet passagescommunicatingitwith the working chamber; a substantial-ly*=lflii-id-*-tight casing enclosing I the said relatively moving partsand' vvith which'communicate the ends -0fthe Working I clearances remotefrom the worhingchamber, vsaid casing 'being 'arranged to befilled-withWorking fluid, and valveapparatusincluding in combinationa'pressure-operated nonreturn valve arranged to-perlet passages tothe-interior'of theca'sing and-a second: -pressure=-operated non-returnvalve arranged to permit flow of fluid from the casing to the other-ofthe said-inlet and outlet passages.

2.-A rotary hydraulic machine comprising relatively-moving partsenclosing a workingchamber with working clearances between therelatively moving pairtsand inletand outlet passages communicating withthe working "chamber," a -sub-- stantiaily fiuidj-tight casing fenclosing said relatively moving parts and :Withwhich communi cateltheends of-ithe said working clearances remote from the working chambensaidcasing being arranged to be filled with working fluid, two pressureoperated non-return admission valves arranged to permit'zflow of fluidinto the casing respectively from" the iinlet and "outlet passages,and-two pressure operate'doutletvalves arranged torupermit 'tflowof'fluid from the casing respectively-to: the inlet and outlet passages.

3. A rotarytzhydrau'lic machine'as claimed in claim '1 in which each ofthe non-return valves is constructed and arranged to open onthe-"occurrence of approximately the same-predetermined'pressuredifference across "it whereby beth' valveswopen'on the occurrence oftwice that pressure difierence between the pressures respectivelyin theinlet andoutlet passages.

14. A.rrotary hydraulic machine as claimed in claim-11in which-each orthe non-return admis- 8 sion/valveszcontrolling:theiflovw ofiifluidiirom" one ofirthasaidrinlet and;.outletzpassagesztoathenasing .gisconstructed: and; arranged:tor.open1at-.substantially-the:same.::pressure idifferenceracrossz fitasxcauseszlthe opening: of the; associated hon -returnzotrtletv'valvecontrollingrthe flow. 10f ifluicl-rto the other of said passages. e

350A: hydraulic system sin'cluding ati dea'stnonehydraulic'machine.asclaimed in claim i in whi'ch the nonreturn: valves!are: constructed to open: at a' pressu-re :whiichds greaterithan thepressure dinposedlthereon whenzthe system isioperating zunder steadyload conditions-what less than the pressure imposed. thereon when the:system is :operating underpeak load conditions.

6 Aghydraulicisysjtem .as claimed in claim 5 'in which each of the nonreturn valves -is constructed and arranged: to;-open. at sub'stantiallythe:sameapressure-ldifference.across' it 'as thatwrequired to .1 causethe: o'ther non return valve -"-to open.

'"7.;-.Axhydraulic system including at least one hydraulimmachine asclaimed in claim" 2"i1'1'Whl0h tha-two non-return*valves which arearranged to open to permit fiowof fluid-through thecasing eachidirection are constructed to open at a pressure which:;is=:greater thanthe pressure imposedr on tithem when the system is operatingunder-steady? :load conditions but less than -that imposed .Onthem.when; the system -iSf operating underzpeak .ioad conditions.

- 8. Aahydraulicssystemi as claimed in claim" Tin which each .of f thenon1-return..--valves *is con-- structeds andrarranged :to open atsubstantially the; seiner-pressure across; rite as that require'd' tocause each of s the Mother non-return valves-to open.

c9.. .A rotary;hydrau1icmachine comprising rela tivelyrrotatingixpartsenclosing between them an annuiarxworking.chamber; one-0tsaidparts-being stationary and including theouter--circumferentiahvvall-oi the working chamber through which passinlet: and outlet passages at oircumierentially spaced points while theother. of said parts rotates and :constitutes :one :end wall of I theWorking chamber and carrieswat leasttwo-spaced blades extending.acrossrrtheiworking chamber, a rotary abutment extending across theworking chamber between the. :inlet and outlet passages and-maka"substantially fiuid-tight*seal-with the :inner andzouter walls-of the.working chamber andhaving blade receiving recessesthereintvhich duringitS'fIDtatiOn.(701118"111130 position to receive the bladestandrpermitthem to pass the abutmenta substantially fluid tight casing enclosingthe relatively -rotatable 'partsand the rotary abutmentz andinto-'which-open the ends of the Workingxclearances'between these partsremote from the working "chamber; and valve apparatus including apressure operated-non-return valve arranged to permit flow of"fiuid"fromone of the said inlet and outlet passages to the interior of the casingand 'a second pressure operated nonreturn 'valve arranged to-permitflow'ofgfiuid from the casing! to the other of' said inlet and outlet ports.

10. A rotary hydraulic machine; as claimed in claim' 9 in which each of'thepressureoperated non-returnvalves-is-arranged to'open on theoccurrence of'substantially the same pressure difference across it.

11. A rotary hydraulic machine as claimed in claim 9 in which four'pressure operated; nonreturn valves are "provided; two: of ,said valves9 casing respectively from the inlet and outlet passages while the othertwo are arranged to permit flow of fluid out of the casing respectivelyto the inlet and outlet passages.

12. A hydraulic system including at least one hydraulic machine asclaimed in claim 9 in which the two non-return valves are constructedand arranged to open at a pressure which is greater l0 ing conditionsdue to leakage through the working clearances of the hydraulic machineat the rotational positions of the parts thereof in which the greatestlength of working clearance is subject to pressure from within theworking chamber.

EDWARD HARRY JOHNSON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 589,462 Bibus Sept. 7, 1897 1,064,169 Prall June 10, 19131,989,387 Vickers Jan. 29, 1935 2,344,879 Johnson Mar. 21, 19442,440,072 Booth Apr.. 20, 1948

